NRC Generic Letter 1991-15
'Io UNITED STATES
0 ?NUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555 September 23, 1991
ADDRESSEES
- ALL POWER REACTOR LICENSEES AND APPLICANTS
SUBJECT: OPERATING EXPERIENCE FEEDBACK REPORT, SOLENOID-OPERATED
VALVE PROBLEMS AT U.S. REACTORS
(GENERIC LETTER 91-15)
of operating This generic letter informs addressees of a case study report by the Office experience problems with solenoid-operated valves (SOVs) prepared published as for Analysis and Evaluation of Operational Data (AEOD) and NUREG-1275, Volume 6, "Operating Experience Feedback Report--Solenoid-Operated integrates what Valve Problems," February 1991 (copy enclosed). The case study extensive assessment has been learned over the past several years and provides an in design and of SOV operating experience. The study describes deficiencies feedback of application, manufacture, maintenance, surveillance testing and attention failure data, and concluded that problems with SOVs need additional are not intended by the industry. While the recommendations in the case study in the to establish regulatory requirements, many of the problems described and quality report already are addressed by current environmental qualification assurance rules.
affected In the study, several events are described in which SOV failuresor multiple redundant safety components, multiple trains of safety systems isolated occurrences safety systems. Three of the most significant events were valves (MSIVs) in involving the failure to close of both main steam isolation diesel generators, the same line, the inability to start two redundant emergency insert. The examples and simultaneous failure of several BWR control rods to to common mode failure illustrate the vulnerability of safety-related equipment of SOVs reliability or degradation of SOYs. The NRC is concerned about theregulator activities, used in safety applications. As part of NRC's ongoing include the inspections such as Safety System Functional Inspections (SSFIs) safety related reliability of SOVs as well as other components required by advice to the Electric Power applications. The NRC also is providing technical Center (NMAC) to Research Institute's (EPRI) Nuclear Maintenance Application The first draft of the SOV
assist in preparing an SOY maintenance guide. end of 1991.
maintenance guide is anticipated to be available towards the use in each It has been estimated that many hundreds of SOVs are in wide-spread indirectly as nuclear power facility. They are used in safety-related systems system fluid (such as pneumatic or hydrau- pilot operators working with control (such as lically operated isolation valves) and directly in fluid systems system for to vent the reactor vessel head or to supply air to the starting nonsafety-related emergency diesel generators). Many SOYs are also used in as plant instrument systems that can significantly affect safety systems (such systems and compo- air drier systems). Over the years, many failures of plant SOV failures, nents have been attributed to SOV problems. To address specific information notices the Nuclear Regulatory Commission (NRC) has issued numerous
9109180200 P DRC osooOcO 3 P
a lo
Generic Letter 91-15 -2- September 23, 1991 and bulletins that provide the immediately attributed root cause for the failure. Because these communications frequently were focused on a specific failure, licensees may have made assessments and taken corrective actions that were focused on the specific failures and not on broader issues.
In the case study, the staff reviewed many SOV failures and degradations and discussed those having a similar failure mechanism, thereby showing how only slight differences frequently are all that separate operation from failure.
Correcting only one obvious and specific deficiency at a time without awareness of other mechanisms for degradation may permit another problem in a short time to lead to unnecessary recurrent SOV failures. In addition, correcting problems only in SOVs used in the specific application in which the problem was found can allow similar SOY degradation to develop in other applications.
No specific action or written response is required by this generic letter.
However, it is expected that recipients will review the information presented in the case study for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. Since this generic letter and enclosure do not contain new or revised regulatory requirements, the Backfit Rule, 10 CFR 50.109, does not apply. If you have any questions about this matter, please contact one of the technical contacts listed below or the appropriate NRR project manager.
Sincerel Ja s G. Partlow As ociate Director for Projects Office of Nuclear Reactor Regulation Enclosure:
NUREG-1275, Volume 6 Technical Contacts: H. Ornstein, AEOD
(301) 492-4439 J. Carter, NRR
(301) 492-1153
LIST OF RECENTLY ISSUED GENERIC LETTERS
Generic Date of Letter No. Subqect Issuance
- - - - - - - - - - - - - - - Issued To
91-14 EMERGENCY TELECOMMUNICA- 09/23/91 ALL HOLDERS OF OP
TIONS LICENSES OR CONST.
PERMITS
91-13 REQUEST FOR INFO RELATED 09/19/91 LICENSEES AND APPLI-
TO RESOLUTION OF G1130, CANTS Braidwood, Byron
"ESSENTIAL SERVICE WATER Catawba, Comanche Peak SYS FAILURES AT MUTLI-UNIT Cook, Diablo, McGuire SITES," PURSUANT TO 10CFR50.54(f)
91-12 OPERATOR LICENSING NAT. 08/27/91 ALL PWR REACTOR
EXAMINATION SCHEDULE AND APPLICANTS FOR
AN OPERATING LICENSE
91-11 RESOLUTION OF GENERIC 07/18/91 ALL HOLDERS OF
ISSUES 48, "LCOs FOR CLASS OPERATING LICENSES
1E VITAL INSTRUMENT BUSES,"
and 49, "INTERLOCKS AND LCOs FOR CLASS 1E TIE BREAKERS"
PURSUANT TO 10CFR50.54(f)
91-10 EXPLOSIVES SEARCHES AT 07/08/91 TO ALL FUEL CYCLE
PROTECTED AREA PORTALS FACILITY LICENSEES
WHO POSSESS, USE,
IMPORT OR EXPORT
FORMULA QUANTITIES
OF STRATEGIC SPECIAL
NUCLEAR MATERIAL
88-20 INDIVIDUAL PLANT EXAMINATION 06/28/91 ALL HOLDERS OF
SUPP. 4 OF EXTERNAL EVENTS (IPEEE) OLs AND CPs FOR
FOR SEVERE ACCIDENT VULNERA- NUCLEAR POWER
BILITIES - 10 CFR 50.54 (f) REACTORS
91-09 MODIFICATION OF SURVEILLANCE 06/27/91 ALL HOLDERS OF
INTERVAL FOR THE ELECTRICAL OLs FOR BWRs PROTECTIVE ASSEMBLIES IN
POWER SUPPLIES FOR THE
91-08 REMOVAL OF COMPONENT LISTS 05/06/91 ALL HOLDERS OF OLs FROM TECHNICAL SPECIFICA- OR CPs FOR NUCLEAR
TIONS POWER REACTORS
91-07 GI-23 "REACTOR COOLANT 05/02/91 ALL POWER REACTOR
PUMP SEAL FAILURES" AND LICENSEES AND